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Highlights: [•] Mn3TeO6 and Co3TeO6 are antiferromagnets with corundum related structures. [•] The structural and magnetic properties of Mn3−x Co x TeO6 ceramics were investigated. [•] All compounds adopt the trigonal structure of Mn3TeO6 up to at least x =2.4. [•] The antiferromagnetic transition temperature monotonously increases with x. [•] NPD data evidences the magnetic structure of the Mn3−x Co x TeO6 ceramics. [Copyright &y& Elsevier]

Abstract: Solid solutions of (1−x)LaFeO3–(x)PbTiO3 (0< x <1) have been prepared by conventional solid-state reaction. These complex perovskites have been studied by means of X-ray (XRPD) and neutron powder (NPD) diffraction, complemented with dielectric, magnetic, heat capacity and Mössbauer measurements. Complete solubility in the perovskite series was demonstrated. The NPD and XRPD patterns were successfully refined as orthorhombic (x ≤0.7) and tetragonal (x ≥0.8). A composition-driven phase transformation occurs within the interval 0.7< x <0.8. The samples with x <0.5 showed evidence of long-range magnetic ordering with an G-type antiferromagnetic arrangement of the magnetic moments of the Fe3+ cations in the B-site with propagation vector k =(0,0,0). Based on the obtained experimental data, a combined structural and magnetic phase diagram has been constructed. The factors governing the structural, dielectric and magnetic properties of (1−x)LaFeO3–(x)PbTiO3 solid solutions are discussed, as well as their possible multiferroicity. [Copyright &y& Elsevier]

The magnetic characteristics of ball-milled Cr and Mn powders were investigated using x-ray and electron microscopy and flame atomic absorption spectrometry. The results showed that the main component of the Mn and Cr powder volume was occupied by alpha-Mn and bcc Cr, respectively. The size of the Cr and Mn particles over the critical milling time of 100 minutes were less than 1 mm.

Abstract: Mn3TeO6 exhibits a corundum-related A3TeO6 structure and a complex magnetic structure involving two magnetic orbits for the Mn atoms [Ivanov et al., 2011 ]. Mn3−x Cd x TeO6 (x=0, 1, 1.5, and 2) ceramics were synthesized by solid state reaction and investigated using X-ray powder diffraction, electron microscopy, and calorimetric and magnetic measurements. Cd2+ replaces Mn2+ cations without greatly affecting the structure of the compound. The Mn and Cd cations were found to be randomly distributed over the A-site. Magnetization measurements indicated that the samples order antiferromagnetically at low temperature with a transition temperature that decreases with increasing Cd doping. The nuclear and magnetic structure of one specially prepared 114Cd containing sample: Mn1.5 114Cd1.5TeO6, was studied using neutron powder diffraction over the temperature range 2–295K. Mn1.5 114Cd1.5TeO6 was found to order in an incommensurate helical magnetic structure, very similar to that of Mn3TeO6 [Ivanov et al., 2011 ]. However, with a lower transition temperature and the extension of the ordered structure confined to order 240(10)Å. [Copyright &y& Elsevier]

Abstract: The complex metal oxide Mn3TeO6 exhibits a corundum related structure and has been prepared both in forms of single crystals by chemical transport reactions and of polycrystalline powders by a solid state reaction route. The crystal structure and magnetic properties have been investigated using a combination of X-ray and neutron powder diffraction, electron microscopy, calorimetric and magnetic measurements. At room temperature this compound adopts a trigonal structure, space group with a =8.8679(1)Å, c =10.6727(2)Å. A long-range magnetically ordered state is identified below 23K. An unexpected feature of this magnetic structure is several types of Mn-chains. Under the action of the incommensurate magnetic propagation vector k =[0, 0, 0.4302(1)] the unique Mn site is split into two magnetically different orbits. One orbit forms a perfect helix with the spiral axis along the c-axis while the other orbit has a sine wave character along the c-axis. [Copyright &y& Elsevier]

Abstract: The perovskite (Bi0.5Pb0.5)(Fe0.5Zr0.5)O3 was synthesized by solid-state reaction in an attempt to find magnetoelectric materials, in which ferroelectricity and ferromagnetism coexist. This complex perovskite has been studied by X-ray and neutron powder diffraction in combination with magnetic measurements. The compound crystallizes in the orthorhombic space group Pbam with a ∼ √2a p, b ∼ 2√2a p and c ∼ 2a p (with a p ∼ 4.057Å). The field and temperature dependence of the magnetization combined with neutron diffraction data showed antiferromagnetic behavior with the Neel temperature, T N ∼ 450K. Rietveld refinements of neutron powder diffraction data collected at different temperatures, between 10 and 700K, have been carried out in order to extract information about the thermal evolution of the nuclear and magnetic structures. A distorted orthorhombic perovskite structure was found within the whole temperature interval. The Bi/Pb and Fe/Zr ions were found to be partially ordered over the perovskite A-site and disordered over the B-site. The neutron diffraction patterns of the (Bi0.5Pb0.5)(Fe0.5Zr0.5)O3 sample showed evidence of a long-range magnetic ordering below T N with a propagation vector k =(0,0,0) and an antiferromagnetic arrangement of the magnetic moments of the Fe3+ cations in the B-site. This is consistent with an Ay-type magnetic structure. The factors governing the structural and magnetic properties of (1− x)BiFeO3–xPbZrO3 solid solutions are discussed and compared with those of pure BiFeO3 and PbZrO3. A solid solution strategy for developing magnetoelectric properties in BiFeO3-based compounds is described, with the aim of realizing both a spontaneous polarization and magnetization at room temperature. [Copyright &y& Elsevier]

Abstract: The structural and magnetic properties of the perovskite Sr2MnSbO6 have been studied. Combining neutron and X-ray powder diffraction data, the temperature evolution of the structural parameters was investigated with the Rietveld method between 2 and 1000K. The crystal structure is tetragonal (space group I4/m) within the temperature interval of 2–750K and cubic (space group Fm-3m) above 750K. Both octahedral B-site positions were found to be partially occupied by Mn and Sb, but with different Mn/Sb ratios. The magnetic susceptibilities showed irreversibility between field cooled and zero-field cooled (ZFC) conditions and spin glass like magnetic dynamics including aging and memory phenomena at temperatures below 30K; all appearing well above a broad maximum at 13K in the ZFC susceptibility curves. This suggests that the material reaches an unconventional spin-glass state at low temperatures, possibly arising from a competitive situation between the double exchange (ferromagnetism) and the super-exchange (antiferromagnetism). Neutron diffraction patterns showed no evidence of a long-range magnetic ordering at 2K which is consistent with spin glass behavior. The factors governing the observed structural and magnetic properties of Sr2MnSbO6 are discussed and compared with those of other quaternary Mn- and Sb-containing perovskites. Graphs of the temperature of magnetic phase transitions as functions of the cation size were constructed and are discussed for the AB3+ 1/2B5+ 1/2O3 series with isomorphous substitution of B3+ and B5+ cations. Possible influence of the A-cation sublattice on magnetic properties is also shortly considered. [Copyright &y& Elsevier]

Abstract: Solid solutions of the perovskites (1− x)BiFeO3–xPbZrO3 with x ranging from 0 to 0.2 were synthesized by solid-state reaction in an attempt to find magnetoelectric materials, in which ferroelectricity and ferromagnetism coexist. These complex perovskites have been studied by X-ray and neutron powder diffractions, magnetic and Mössbauer spectroscopic measurements. All samples are single phase with rhombohedrally distorted perovskite structure. The field and temperature dependences of the magnetization of (1− x)BiFeO3–xPbZrO3 samples showed antiferromagnetic behavior with Neel temperatures, T N =635K (x =0.1) and 500K (x =0.2); a weak ferromagnetic moment appeared at T N in both samples reaching about 0.01μB/Fe at low temperature for the x =0.1 sample. Mössbauer spectra also support the existence of the magnetic order and are consistent with the presence of high-spin Fe3+ cations located in the octahedral B-site position. Rietveld refinements of neutron powder diffraction data collected at different temperatures, between 10 and 700K, have been carried out. The structure of these compounds is a rhombohedrally distorted perovskite (space group R3c) within the whole temperature interval. The Bi/Pb and Fe/Zr ions were found to be disordered over the perovskite A- and B-sites, respectively. Neutron diffraction patterns showed evidence of a long-range magnetic ordering below T N with a G-type antiferromagnetic arrangement of the magnetic moments of Fe3+ cations in the B-site. The effect of PbZrO3 doping on BiFeO3 results in a noticeable lattice expansion and a significant decrease of T N. The factors governing the observed structural and magnetic properties of (1− x)BiFeO3–xPbZrO3 are discussed and compared with those of pure BiFeO3. [Copyright &y& Elsevier]

Abstract: The structural and magnetic properties of the complex metal oxides Pb(Mn1/2Nb1/2)O3 (PMNO) and Pb(Mn1/4Fe1/4Nb1/2)O3 (PMFNO), which belong to a class of disordered perovskites have been studied. The magnetic susceptibilities of PMNO showed hysteresis between field cooled and zero-field cooled conditions below the transition of 15K, suggesting that the material has a spin-glass feature. Neutron diffraction patterns of PMNO showed no evidence of a long-range magnetic ordering at 1.5K, which is consistent with spin-glass behavior. Rietveld refinements of neutron powder diffraction data collected at different temperatures between 1.5 and 700K have been carried out in order to extract structural information. The crystal structure of this compound is cubic (space group Pm m) within the whole temperature interval. The Mn and Nb ions were found to be disordered over the perovskite B-sites. The main feature of this structure is the positional disorder at the Pb site, the importance of which in connection with the ferroic transitions is briefly discussed. The Pb cations show a positional disorder shifting from their high-symmetry positions along the [111] direction. The effect of Fe-doping on PMNO has been studied. The substitution of Fe at the Mn site in PMFNO results in a small changes of the magnetic properties without significant differences in the crystal structures. The factors governing the observed structural and magnetic properties of PMNO and PMFNO are discussed and compared with those of other quaternary Mn-containing perovskites. For the PbB3+ 1/2Nb1/2O3 series with the isomorphous substitution B3+, graphs of average lattice parameters of the perovskite phase and the temperatures of ferroelectric and magnetic phase transitions as functions of the B3+ cation radius were constructed and are discussed. Influence of A-cation sublattice on magnetic properties is also considered. [Copyright &y& Elsevier]

Abstract: The complex perovskite lead iron tungsten niobium oxide, Pb(Fe0.6W0.2Nb0.2)O3 (PFWN) which belongs to the class of disordered magnetoelectrics, has been studied by X-ray and neutron powder diffraction, magnetic and Mössbauer spectroscopic measurements. Structural, dielectric and magnetic properties of PFWN are presented and reviewed. Magnetic measurements indicate that the most important interactions are of antiferromagnetic nature yielding T N =300K, however, with indications of a reentrant spin glass behaviour below 20K. The parameters of Mössbauer spectra also support the existence of the magnetic order and are consistent with the presence of high-spin Fe3+ cations located in the octahedral B-site. Rietveld refinements of diffraction data at different temperatures between 10 and 700K have been carried out. The long-range structure of PFWN is cubic (space group Pm−3m) over the whole temperature interval. The Fe, W and Nb cations were found to be disordered over the perovskite B-sites. The Pb cations show a position disorder along the 〈111〉 direction shifting from their high-symmetry position. At the temperatures below T N, an antiferromagnetic arrangement of the magnetic moments of Fe3+ cations in the B-site is proposed in accordance with the antiferromagnetic properties of PFWN. The factors governing the observed nuclear and magnetic structures of PFWN are discussed and compared with those of pure Pb(Fe0.67W0.33)O3, Pb(Fe0.5Nb0.5)O3 and other quaternary Pb-based perovskites containing iron. [Copyright &y& Elsevier]

Abstract: A study of the crystallographic and magnetic structures of the double perovskite Sr3Fe2TeO9 has been carried out on a polycrystalline sample using neutron powder diffraction (NPD) data between 10 and 650K. An analysis of the NPD patterns at room temperature has shown that this compound crystallises in the tetragonal space group I4/m with a =5.5614(7)Å and c =7.867(1)Å and has a partially ordered arrangement of Fe and Te at the B-sites. The compound undergoes an I4/m → Fm-3m improper ferroelectric phase transition near 460K. A low-temperature ferrimagnetic ordering (below T N =260K) has been followed from the magnetisation measurements and sequential NPD data analysis. In good agreement with magnetic measurements the ferrimagnetic structure with very weak magnetisation is defined by the propagation vector k =(0, 0, 0). In addition to the obtained experimental results on magnetic and electric properties some aspects of magnetoelectricity in this perovskite are also discussed and compared with those of another quaternary oxide Sr3Fe2B6+O9. [Copyright &y& Elsevier]

Abstract: The magnetic and structural properties of oxygen-deficient perovskites with composition Ba3Fe2WO9− δ (BFWO) have been systematically studied for two different oxygen contents corresponding to and in the chemical formula in order to determine and correlate their chemical composition, structural and magnetic properties. The evolution of nuclear and magnetic structures with temperature has been investigated by neutron powder diffraction. It was shown that at room temperature the stoichiometric compound () adopts a hexagonal 6H-perovskite structure (space group ). This phase, when heated at high temperature under a stream of Ar gas, transforms to an oxygen-deficient phase ), which is an ordered cubic perovskite structure (space group ). The crystallographic and magnetic properties of the obtained phases are compared, and it is clear that the magnetic properties are significantly affected by oxygen non-stoichiometry. These changes of magnetic properties for such a slight decrease in oxygen content are interpreted as a result of structural transformations. Together with the experimental results based on neutron powder diffraction data a discussion of some aspects of the structural transformation () is presented. [Copyright &y& Elsevier]

Abstract: A study of the crystallographic and magnetic structure of the double perovskite Sr2CoMoO6 (SCMO) has been carried out on a polycrystalline sample using neutron powder diffraction (NPD) data between 10 and 700K. An analysis of the NPD patterns at room temperature has shown that this compound crystallises in the tetragonal space group I4/m with a =5.5616(1)Å and c =7.9470(2)Å and has a 1:1 ordered arrangement of Co and Mo at the B-sites. This compound undergoes a I4/m → Fm3m improper ferroelectric phase transition near 560K. A low-temperature antiferromagnetic ordering (below T N =36K) has been followed from sequential NPD data analysis. The antiferromagnetic structure is defined by the propagation vector k =(1/2, 0, 1/2). In addition to the obtained experimental results on magnetic and electric properties some aspects of magnetoelectricity in this perovskite are also discussed. [Copyright &y& Elsevier]

Abstract: The structural properties of complex perovskite lead iron tungstate, Pb(Fe2/3W1/3)O3 (PFW) which belongs to a class off disordered magnetoelectrics has been studied by neutron powder diffraction. Rietveld refinement of neutron powder diffraction data collected at different temperatures, between 10 and 700K, have been carried out in order to extract structural information. The long-range structure of PFW is a cubic one (space group Pmm) within the whole temperature interval. The PFW sample demonstrated very low thermal expansion at lower temperatures. The iron and tungsten ions were found to be disordered over the perovskite B-sites. Pb cations show a position disorder shifting from their high-symmetry positions along the [111] direction. Furthermore, in order to obtain a good agreement with experiment at low temperatures, below TN, it was necessary to assign non-zero magnetic moments to the iron ions, these being in a co-linear antiferromagnetic arrangement in accordance with the antiferroelectric properties of PFW. The magnetic structure can be described with a doubling of the unit cell axes. The factors governing the observed nuclear and magnetic structures of PFW are discussed and compared with those of other quaternary iron-containing perovskites. [Copyright &y& Elsevier]

The complex perovskite with composition Ba3Fe2WO9 (BFWO) has been synthesised, and the evolution of nuclear and magnetic structures with temperature has been investigated by neutron powder diffraction. It was shown that at room temperature this compound adopts the 6H-perovskite structure, space group P63/mmc (a=5.7584(2) A˚, c=14.1019(9) A˚), in which the cation sites within the face-sharing octahedra are occupied by Fe and W cations and those within the corner-sharing octahedra are occupied by Fe exclusively. The magnetic diffraction peaks were registered at low temperatures and a possible model for the magnetic structure was proposed in accordance with the ferrimagnetic properties of BFWO. The magnetic structure can be described as an array of ferromagnetic layers of Fe moments along the c-axis, and adjacent layers coupled antiferromagnetically. Structural and magnetic features of this compound are discussed and compared with those of other quaternary oxides adopting the 6H-perovskite structure. [Copyright &y& Elsevier]